1. Field of the Invention
The present invention relates to asymmetric data transmission apparatuses, and more particularly, to an asymmetric digital subscriber line transceiver unit-card (ATU-C) in which power is not supplied to a modem that is not connected to a subscriber, and a method of controlling the same.
2. Description of the Related Art
Asymmetric digital subscriber line (ADSL) relates to a new technology for transmission developed by Bellcore (USA). ADSL enables downward transmission of data, for example, from a telephone office to a subscriber, at a rate of 1.5-8 Mbps. Further, ADSL provides for an upward transmission, for example, from the subscriber to the telephone office at a low rate using conventional twisted-pair phone cables. ADSL technology is based on a technique for frequency division multiplexing (FDM). In such an FDM technique, a 1.5 Mbps down-channel is constituted at a frequency band higher than a 4 KHz voice band, and a 16 Kbps up-channel is constituted between the down-channel frequency band and the voice band. Analog voice calls are transmitted over the lowest frequency band.
ADSL utilizes conventional twisted-pair phone cables. This ensures that a transmission distance of sufficient length is provided to allow direct connection between a telephone office or a remote station and a subscriber, without relay. Also, installing a service system for using ADSL is as convenient as installing a conventional plain-old-telephone service (POTS). Further, a frequency band carrying video and control signals is allocated above the frequency band carrying conventional phone signal. Such an allocation ensures that various signals can be transmitted at the same time over a phone line without overlap of frequency bands. ADSL. Likewise, an ATU-Remote (ATU-R), which acts as a transmission unit, is connected to the subscriber end of the ADSL. The ATU-R and a conventional telephone set are directly connected to a personal computer (PC), a synchronous transfer mode (ATM) or local area network (LAN) console, or to a video/audio signal decoder. The video/audio signal decoder is referred to as xe2x80x9cset-top boxxe2x80x9d. Such a set-top box is connected to a television (TV) receiver or PC. As mentioned, the ADSL system can be connected to an ATM network.
With the increased use of ADSL modems, an owner of a public network will expand concurrently by building up the ATM backbone of the network. The will further enable subscribers to use ADSL modem.
FIG. 1 is a block diagram showing the structure of an a synchronous data transmission apparatus. In FIG. 1, reference numeral 100 represents a device installed at the telephone office end (hereinafter, referred to as an ADSL device for the telephone office), and reference numerals 28a-28n represent devices installed at the subscriber end (hereinafter, referred to as an ADSL device for subscriber). The ADSL device for the telephone office 100 includes a network interface and control card 10 for interfacing with a data bus on one side and a high-speed data network on the other, a maintenance and repair management unit 12. A plurality of ATU-Cs, 18a through 18n, are connected to the data bus on one side and a plurality of ADSL devices, for use by subscribers, on the other.
A plurality of modems (not shown) for the ADSL are installed in each of the ATU-Cs 18a through 18n. These modems allow connection to the plurality of ADSL devices intended for use by subscribers. Upon supply of power to the ATU-Cs 18a through 18n, power is also simultaneously applied to all the modems. Further, the system monitors whether a subscriber requests connection to a phone line.
However, it is expected that most of the time, not all of the modems associated with the ATU-Cs will be allocated to subscribers. In particular, when a subscriber disconnects, a corresponding modem that becomes unallocated because of the termination of the connection, continues to consume power. Also, in the case of increasing the number of ATU-Cs, the modems corresponding to the new ATU-Cs may remain free for some time before they are allocated to subscribers.
However, because power is simultaneously applied to all the models corresponding to the ATU-Cs, unnecessary power consumption increases in proportion to the number of unallocated modems. Such a waste of power increases the amount of heat generated in the ADSL device for the telephone office, and deteriorates the ATU-C.
An object of the present invention is to provide an asymmetric digital subscriber line transceiver unit-card (ATU-C) capable of optimizing the use of power by supplying power only to modems that are allocated to a subscriber.
Another object of the present invention is to provide a method of controlling the ATU-C.
According to an aspect of the present invention, there is provided an asymmetric digital subscriber line transceiver unit-card (ATU-C) comprising: a plurality of modems, that can be connected to a plurality of asymmetric digital subscriber line transceiver unit-remote (ATU-R) for subscribers; a plurality of power switches for selectively supplying power to the plurality of modems; and a microprocessor for controlling an operation of the plurality of power switches.
Preferably the ATU-C further comprises a power supply unit, wherein power is supplied to the plurality of modems using the power supply unit.
Preferably the microprocessor controls the operation of the plurality of power switches based on a connection status between subscribers and the plurality of modems.
Preferably the plurality of power supply switches supply power to the plurality of modems in response to signals from the microprocessor.
Preferably the ATU-C further comprises a maintenance and repair management unit for coordinating with the microprocessor in managing maintenance and repair of the ATU-C.
Preferably power supply can be interrupted for each of said plurality of modems for testing.
Still preferably the microprocessor obtains information on the connection status of the plurality of modems and the subscribers by querying the maintenance and repair management unit.
Still preferably a user is provided the ability to cut off and resupply power to each of said plurality of modems through the maintenance and repair management unit for testing.
Another aspect of the present invention is a method of controlling an asymmetric digital subscriber line transceiver unit-card (ATU-C) including a power supply unit; a plurality of modems that can be connected to a plurality of asymmetric digital subscriber line transceiver unit-remote (ATU-R) for subscribers; a plurality of power switches for selectively supplying power generated by the power supply unit to the modems; and a microprocessor for controlling the operation of the power switches depending on the connection status between the subscribers and the modems, the method comprising: initializing the ATU-C after power is supplied to the ATU-C, by initializing the power switches to an off state in which power is not applied to the plurality of modems; and controlling the power switches depending on the connection status between the subscribers and the modems, to supply power only to a subset of the plurality of modems that are allocated to subscribers.